Valve-detector for wireless.



G. W. PICKARD. VALVE DETECTOR FOR WIRELESS.

APPLICATION FILED JULY 3,1912.

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ennnivr' wHI'r'rInn rIcKAnn, or AMEsBUnY, MASSACHUSETTS, ASSIGNOR ro WIESS srnoIAL'rY APPARATUS COMPANY, on BOSTON, MAssAcHUsETrs, A

CORJPO '5 t 'I'ION OF NEW "YORK.

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Specification of Letters Patent.

Patented lBeb. lib, third.

To all whom it may concern:

Be it known that I, GREENLEAF WHrrTmR PICKARD, a citizen of the United States of America, and a resident of Amesbu'ry,

assachusetts, have invented certain new and useful Improvements in Valve-Detectors for Wireless, the principles of which are set forth in the following specification and accompanying drawing, which disclose the form of the invention which I now conslider to be the best of the various forms in which the principles of the invention may be embodied. y

This invention relates to wireless detectors of the rectifier type embodying the well lmown Edison efi'ect of uni-lateral electrical conduction between hot and cold terminals, and commonly termed valves or audions in the commercial art. All prior forms of this detector have consisted of an exhausted glass tube, containing a heated terminal in the form of a small incandescent lamp filament, and one or more cold terminals, in the form of plates, grids, etc. All of these prior forms have been subject, by virtue of their construction, to a most serious detect, 6. a, inoperativeness by temporary loss of sensitiveness when exposed to static disturbances, such as are daily experienced in commercial wireless working, particularly in the tropics. I have carefully investigated this loss of sensitiveness, and have discovered that it is in some way caused by an accumulation of static I charge on the interior wall of the glass bulb;

and I have also discovered how to prevent the trouble. Apparantly the stream of negative ions passing from the hot to, the cold terminal is in some way momentarily scattered or diverted by an excessive rush of current, caused by static, so that instead of substantially all the ions. reaching the cold terminal, a very material part of them reaches the wall of the dielectric :bulb,

1 building up therein a static charge; In some way, which I do not now know, this static charge renders the detector practlcally 1noperative untilitcanbe discharged, and the operator loses a word or two of the message he is receiving. In working in tropical climates or seasons, these lnterruptlons are mtolerable, as. they occurseveral times a m nebject of? e invtion is to prevent invention consists of the herein-described means for accomplishing that object;

The drawings show the application of my invention to one of the various forms of valves or audions, The detector itself is here shown in section, approximately to scale.

The external wireless circuits of Figure 1 are diagrammatic, and shown by way of example, and the detector may be used with any desired and suitable circuits. Fig. 2 is a section of one simple form of the various possible embodiments.

The hot and cold terminals, '5. 6-, the filament A and the plate B, are provided in the customary manner wit hsuitable leads 0, P, andQ respectively, sealed in the glass bulb E. The surface of the glass stalk N of bulb E, which stalk supports the upper ends of said leads or detector terminals, is covered (Fig. 1) with a conducting layer D, which may be a deposit of silver or othermetal. This deposit or layer D is continuous, except that it is cut away in minute circles S, T, U, immediately surrounding the leading in wires 0, P, Q, So that these are not shortcircuited by said conducting layer I). It is important, however, that no substantial amount of glass be exposed at these points, for this would form to that extent a dielectric surface for the .lodgment of static air-tight bulb E be also employed. Chamber Can'd layer lD constitute a conducting sheath which substantially incloses termi nals A, B, and; provides means for collecting substantially all the negative ions which may becaused tobe scatteredin passing from the hot to the cold terminal. A lead It is connected to this sheath, either 'to'conducting layer D or to the conducting chamber'G, '(or both, as shown, if they are not in good contact), and connected to a ground or other leading-away connection K. A glass or other air ti the chamber and the-space w; 1-. 1-; b

ht bulbEv may be paced over which I have 'hausted to a good vacuum. The outer bulb or vessel E is not essential, although this is probably the best form for the following constructional reasons. If the bulb E is not used, the conducting chamber C should then form as nearly as is possible an air tight joint with the stalk N, and the inclosure exhausted -in the usual manner; but owing to the difliculty. of making an air-tight joint between chamber C and stalk N, the form shown, employing outer air-tight bulb E, is the easiest to construct.

The invention is directed particularly to the substantially complete inclosure of the hot and cold terminals by the complete conducting sheath C, D; and in Fig. 1 it ineludes particularly a substantial closure oi the upper end of chamber 0, and also as nearly a complete closure as is permitted by the entranceof the leads 0, P, Q, of that part of layer D which is exposed to. the interior of chamber G. The above applies also to Fig. 2, wherein sheath C, D is replaced by sheath C 2'. e., a silver plating or deposit on the entire interior surface of glass bulb E,.save for the removal of little specks of the metallic deposit at S, T, U -(as in Fig. 1) around the leading-in wires 0, P,

The reason for the importance of the substantially complete closure, lies in the fact discovered, that the tendency of the ions, under the conditions of static disturbance, is to scatter away from all surfaces into free space, such that not even surface has an attraction for them, although if it lies in their path, it will conduct them away or at least prevent them from rendering the detector inoperative. Thus, if the metallic closure be I not substantially complete, but have any substantial opening, the same constitutes a leak to the dielectric E fora material part of the ions. They have to be positively stopped substantially in all possible directions, and thence discharged from the detector.

When bulb E is employed in the Fig. 1

form,'an air leak is left at the joint between chamber C and layer D, in order to permit the exhaustion of the air from inside chamber C, This leak, however, being between metal walls, lying close together, does not permit the escape of the scattered ions. This joint is not involved in the simple Fig. 2 form.

This detector is connected to any oscillation receiving circuit in the usual manner.

As shown in the drawing, oscillations are a metallic.

impressed upon the terminals G, H by the transmitted ether waves, and through the transformer F the oscillations are transferred to the circuit of the rectifier detector. The hot terminal A is heated by the battery L through the leadsO, P, and is also connected to one terminal of the secondary of transformer F. The cold terminal B is connected through the lead Q through a local battery M and a telephone receiver J, (preferably shunted by a condenser I), to the other terminal of the secondary of transformer F. The local battery M, while not essential to the operation of this detector, gives enhanced sensitiveness.

The operation is as follows: Oscillatory currents flowing through transformer F are impressed upon hot and cold terminals A, B. As the conduction across the vacuous space between these terminals is unilateral, (only the negative currents passing from A to B), the oscillations are rectified, and cause a signal in telephone J, in the well known manner common to all rectifier detectors. A sudden discharge of static may cause a scattering of negative ions, but those reach and collect on the conducting walls of the special sheath of this invention, are at once carried away, and cannot build up a disturbing static charge. The conducting sheath, or that part of it, which is supported on the bulb E, may be applied thereto in any suitable way, not only by a plating or deposit, as above, but by applying a conducting paint, or in any other desired manner.

I claim:

1. A rectifier detector of the Edison-effect type, which comprises hot and cold terminals and an electrically conducting sheath substantially completely surrounding the same.

2. A rectifier detector of the Edison-effect type, comprising hot and cold terminals, a dielectric container for the same, and an electrically conductin sheath supported by said container and 'su stantially completely surrounding said terminals.

3. A rectifier detector of the Edison-effect type, which comprises hot and cold ter1ni- (murmur WHITTIER PICKARI).

Witnesses:

J. A. Pnoo'ron, H. N. Comm. 

